1. Field of the Invention
This invention relates to a knapsack, more particularly to a knapsack which can be produced at a relatively low cost, which permits air ventilation when carried on a user""s back, and which can massage the user""s back.
2. Description of the Related Art
Conventional knapsacks are mostly made from fabric or polyurethane rubber materials in order to provide comfort during use. While such knapsacks permit air ventilation and are comfortable when placed in contact with a user""s back due to their softness, these materials are relatively expensive. Moreover, these knapsacks require hard support boards placed therein or supportive reinforcement strips formed therearound in order to prevent the contents from being damaged or piled up disorderly and the deformation of the knapsacks. In addition, since such knapsacks require extra time for sewing, the production costs are increased as well. Furthermore, damaged or broken knapsacks that are made from fabric or polyurethane rubber materials could not be easily recycled. Hence, a serious problem in environmental protection arises therefrom.
Therefore, the object of the present invention is to provide a knapsack which can be produced at a relatively low cost, which permits air ventilation when carried on a user""s back, and which can massage the user""s back.
A knapsack according to this invention comprises a sack body defining an accommodation space for receiving articles therein, and including a back wall which has a front wall surface confronting said accommodation space, and a rear wall surface opposite to the front wall surface and adapted to face toward a user""s back; and a plurality of spacers which are disposed on said rear wall surface, which are spaced apart from each other, and which extend away from said front wall surface so as to space said rear wall surface apart from the user""s back, said spacers being molded integrally with said back wall to form a single-piece construction.